Project description:Gene expression profiling of various cell lineages has provided invaluable insights into the molecular mechanisms regulating cellular development and differentiation. However, in vivo molecular profiling of rare and interspersed cell populations, such as endothelial cells, has remained challenging. We have generated a versatile floxed translating ribosome affinity purification (TRAP) mouse model, mCherryTRAP, for Cre-dependent translational profiling of distinct cell lineages from intact tissues. To identify cell type-specific transcripts using TRAP, the data have to be filtered to remove both background transcripts not expressed in the profiled cell type and transcripts expressed in all cell populations of the tissue/organ. Filtering has previously been achieved using transcribed RNA from the tissue/organ. Using the mCherryTRAP model, we demonstrate extensive differential expression of RNAs between the translatome and transcriptome of embryonic brains and kidneys. We evaluate the implications of these data for TRAP studies of abundant and rare cell populations. Finally, we demonstrate the applicability of the technology to study organ-specific endothelial cell differentiation.
Project description:Here we report the expansion of the genetic code of Mus musculus with various unnatural amino acids including N?-acetyl-lysine. Stable integration of transgenes encoding an engineered N?-acetyl-lysyl-tRNA synthetase (AcKRS)/tRNAPyl pair into the mouse genome enables site-specific incorporation of unnatural amino acids into a target protein in response to the amber codon. We demonstrate temporal and spatial control of protein acetylation in various organs of the transgenic mouse using a recombinant green fluorescent protein (GFPuv) as a model protein. This strategy will provide a powerful tool for systematic in vivo study of cellular proteins in the most commonly used mammalian model organism for human physiology and disease.
Project description:BACKGROUND: The classical view on eukaryotic gene expression proposes the scheme of a forward flow for which fluctuations in mRNA levels upon a stimulus contribute to determine variations in mRNA availability for translation. Here we address this issue by simultaneously profiling with microarrays the total mRNAs (the transcriptome) and the polysome-associated mRNAs (the translatome) after EGF treatment of human cells, and extending the analysis to other 19 different transcriptome/translatome comparisons in mammalian cells following different stimuli or undergoing cell programs. RESULTS: Triggering of the EGF pathway results in an early induction of transcriptome and translatome changes, but 90% of the significant variation is limited to the translatome and the degree of concordant changes is less than 5%. The survey of other 19 different transcriptome/translatome comparisons shows that extensive uncoupling is a general rule, in terms of both RNA movements and inferred cell activities, with a strong tendency of translation-related genes to be controlled purely at the translational level. By different statistical approaches, we finally provide evidence of the lack of dependence between changes at the transcriptome and translatome levels. CONCLUSIONS: We propose a model of diffused independency between variation in transcript abundances and variation in their engagement on polysomes, which implies the existence of specific mechanisms to couple these two ways of regulating gene expression.
Project description:BACKGROUND: Long terminal repeat (LTR) retrotransposons make up a large fraction of the typical mammalian genome. They comprise about 8% of the human genome and approximately 10% of the mouse genome. On account of their abundance, LTR retrotransposons are believed to hold major significance for genome structure and function. Recent advances in genome sequencing of a variety of model organisms has provided an unprecedented opportunity to evaluate better the diversity of LTR retrotransposons resident in eukaryotic genomes. RESULTS: Using a new data-mining program, LTR_STRUC, in conjunction with conventional techniques, we have mined the GenBank mouse (Mus musculus) database and the more complete Ensembl mouse dataset for LTR retrotransposons. We report here that the M. musculus genome contains at least 21 separate families of LTR retrotransposons; 13 of these families are described here for the first time. CONCLUSIONS: All families of mouse LTR retrotransposons are members of the gypsy-like superfamily of retroviral-like elements. Several different families of unrelated non-autonomous elements were identified, suggesting that the evolution of non-autonomy may be a common event. High sequence similarity between several LTR retrotransposons identified in this study and those found in distantly-related species suggests that horizontal transfer has been a significant factor in the evolution of mouse LTR retrotransposons.
Project description:Spinal muscular atrophy (SMA) is the most common genetic cause of infant mortality, with an incidence of around 1 in 6,000-10,000 live births. SMA is caused by low levels of full-length survival of motor neuron protein (SMN). Approximately 95% of SMA cases in humans are caused by homozygous deletion of SMN1, with a smaller number caused by discrete mutations within the gene. In concert with other RNA binding proteins, SMN forms complexes both in the nucleus and the cytoplasm of neurons. As such, SMN protein has housekeeping roles in the assembly of ribonucleoprotein (RNP) complexes. In addition, SMN localises to dendrites, synapses and axons in vivo and in vitro, where it is part of messenger RNP (mRNP) complexes with well-known roles in the transport of mRNA. These cellular processes are tightly linked to local translation, suggesting that SMN may play a pivotal role in its regulation. We employed next generation sequencing (NGS) to identify and quantify RNAs associated with polysomes (POL-Seq) in parallel with total cytoplasmic RNA (RNA-Seq) in an established mouse model of severe SMA at both early and late-symptomatic stages. This approach enables the simultaneous identification of variations in RNA populations at both translatome (RNAs engagement with polysomes) and transcriptome (steady state cytoplasmic RNAs) levels. Keywords: motor neuron disease, spinal muscular atrophy, SMA,SMN, translation, polysome profiling, POL-Seq, RNA-Seq Overall design: We extracted both total cytoplasmic and polysomal RNAs from pooled sucrose fractions from early-symptomatic and late-symptomatic brains of SMA mice, as well as from littermate controls. Experiments were performed in biological triplicate for late-symptomatic mice, and in biological duplicate for early-symptomatic mice, for a total of 20 samples.
Project description:Copy number variation is an important dimension of genetic diversity and has implications in development and disease. As an important model organism, the mouse is a prime candidate for copy number variant (CNV) characterization, but this has yet to be completed for a large sample size. Here we report CNV analysis of publicly available, high-density microarray data files for 351 mouse tail samples, including 290 mice that had not been characterized for CNVs previously.We found 9634 putative autosomal CNVs across the samples affecting 6.87% of the mouse reference genome. We find significant differences in the degree of CNV uniqueness (single sample occurrence) and the nature of CNV-gene overlap between wild-caught mice and classical laboratory strains. CNV-gene overlap was associated with lipid metabolism, pheromone response and olfaction compared to immunity, carbohydrate metabolism and amino-acid metabolism for wild-caught mice and classical laboratory strains, respectively. Using two subspecies of wild-caught Mus musculus, we identified putative CNVs unique to those subspecies and show this diversity is better captured by wild-derived laboratory strains than by the classical laboratory strains. A total of 9 genic copy number variable regions (CNVRs) were selected for experimental confirmation by droplet digital PCR (ddPCR).The analysis we present is a comprehensive, genome-wide analysis of CNVs in Mus musculus, which increases the number of known variants in the species and will accelerate the identification of novel variants in future studies.
Project description:BACKGROUND:Identification of protein-protein interactions is an important first step to understand living systems. High-throughput experimental approaches have accumulated large amount of information on protein-protein interactions in human and other model organisms. Such interaction information has been successfully transferred to other species, in which the experimental data are limited. However, the annotation transfer method could yield false positive interologs due to the lack of conservation of interactions when applied to phylogenetically distant organisms. RESULTS:To address this issue, we used phylogenetic profile method to filter false positives in interologs based on the notion that evolutionary conserved interactions show similar patterns of occurrence along the genomes. The approach was applied to Mus musculus, in which the experimentally identified interactions are limited. We first inferred the protein-protein interactions in Mus musculus by using two approaches: i) identifying mouse orthologs of interacting proteins (interologs) based on the experimental protein-protein interaction data from other organisms; and ii) analyzing frequency of mouse ortholog co-occurrence in predicted operons of bacteria. We then filtered possible false-positives in the predicted interactions using the phylogenetic profiles. We found that this filtering method significantly increased the frequency of interacting protein-pairs coexpressed in the same cells/tissues in gene expression omnibus (GEO) database as well as the frequency of interacting protein-pairs shared the similar Gene Ontology (GO) terms for biological processes and cellular localizations. The data supports the notion that phylogenetic profile helps to reduce the number of false positives in interologs. CONCLUSION:We have developed protein-protein interaction database in mouse, which contains 41109 interologs. We have also developed a web interface to facilitate the use of database http://lgsun.grc.nia.nih.gov/mppi/.
Project description:Transcriptome profiling is widely used to infer functional states of specific cell types, as well as their responses to stimuli, to define contributions to physiology and pathophysiology. Focusing on microglia, the brain's macrophages, we report here a side-by-side comparison of classical cell-sorting-based transcriptome sequencing and the 'RiboTag' method, which avoids cell retrieval from tissue context and yields translatome sequencing information. Conventional whole-cell microglial transcriptomes were found to be significantly tainted by artifacts introduced by tissue dissociation, cargo contamination and transcripts sequestered from ribosomes. Conversely, our data highlight the added value of RiboTag profiling for assessing the lineage accuracy of Cre recombinase expression in transgenic mice. Collectively, this study indicates method-based biases, reveals observer effects and establishes RiboTag-based translatome profiling as a valuable complement to standard sorting-based profiling strategies.
Project description:Rodent herpesviruses such as murine cytomegalovirus (host, Mus musculus), rat cytomegalovirus (host, Rattus norvegicus), and murine gammaherpesvirus 68 (hosts, Apodemus species) are important tools for the experimental study of human herpesvirus diseases. However, alphaherpesviruses, roseoloviruses, and lymphocryptoviruses, as well as rhadinoviruses, that naturally infect Mus musculus (house mouse) and other Old World mice are unknown. To identify hitherto-unknown rodent-associated herpesviruses, we captured M. musculus, R. norvegicus, and 14 other rodent species in several locations in Germany, the United Kingdom, and Thailand. Samples of trigeminal ganglia, dorsal root ganglia, brains, spleens, and other organs, as well as blood, were analyzed with a degenerate panherpesvirus PCR targeting the DNA polymerase (DPOL) gene. Herpesvirus-positive samples were subjected to a second degenerate PCR targeting the glycoprotein B (gB) gene. The sequences located between the partial DPOL and gB sequences were amplified by long-distance PCR and sequenced, resulting in a contiguous sequence of approximately 3.5 kbp. By DPOL PCR, we detected 17 novel betaherpesviruses and 21 novel gammaherpesviruses but no alphaherpesvirus. Of these 38 novel herpesviruses, 14 were successfully analyzed by the complete bigenic approach. Most importantly, the first gammaherpesvirus of Mus musculus was discovered (Mus musculus rhadinovirus 1 [MmusRHV1]). This virus is a member of a novel group of rodent gammaherpesviruses, which is clearly distinct from murine herpesvirus 68-like rodent gammaherpesviruses. Multigenic phylogenetic analysis, using an 8-kbp locus, revealed that MmusRHV1 diverged from the other gammaherpesviruses soon after the evolutionary separation of Epstein-Barr virus-like lymphocryptoviruses from human herpesvirus 8-like rhadinoviruses and alcelaphine herpesvirus 1-like macaviruses.
Project description:The mammalian vomeronasal organ (VNO) expresses two G-protein coupled receptor gene families that mediate pheromone responses, the V1R and V2R receptor genes. In rodents, there are ~150 V1R genes comprising 12 subfamilies organized in gene clusters at multiple chromosomal locations. Previously, we showed that several of these subfamilies had been extensively modulated by gene duplications, deletions, and gene conversions around the time of the evolutionary split of the mouse and rat lineages, consistent with the hypothesis that V1R repertoires might be involved in reinforcing speciation events. Here, we generated genome sequence for one large cluster containing two V1R subfamilies in Mus spretus, a closely related and sympatric species to Mus musculus, and investigated evolutionary change in these repertoires along the two mouse lineages.We describe a comparison of spretus and musculus with respect to genome organization and synteny, as well as V1R gene content and phylogeny, with reference to previous observations made between mouse and rat. Unlike the mouse-rat comparisons, synteny seems to be largely conserved between the two mouse species. Disruption of local synteny is generally associated with differences in repeat content, although these differences appear to arise more from deletion than new integrations. Even though unambiguous V1R orthology is evident, we observe dynamic modulation of the functional repertoires, with two of seven V1Rb and one of eleven V1Ra genes lost in spretus, two V1Ra genes becoming pseudogenes in musculus, two additional orthologous pairs apparently subject to strong adaptive selection, and another divergent orthologous pair that apparently was subjected to gene conversion.Therefore, eight of the 18 (~44%) presumptive V1Ra/V1Rb genes in the musculus-spretus ancestor appear to have undergone functional modulation since these two species diverged. As compared to the rat-mouse split, where modulation is evident by independent expansions of these two V1R subfamilies, divergence between musculus and spretus has arisen more by mutations within coding sequences. These results support the hypothesis that adaptive changes in functional V1R repertoires contribute to the delineation of very closely related species.